Looking into the Starmate 5 Dock & Play Radio + PowerConnect™ Vehicle Kit and XMp3i™ Portable Radio with Home Kit.
One I can move from home to any car. I have an fm transmitter for cars without a mp3 slot.
Comments welcome on your experiences with the radios and services.
On our trip to Seattle area last year the rental included one. Worked well traveling around and avoiding changing stations. Even on the Olympic Coast, we didn't get a lot of signal loss.